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SimpleChemist-238
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[*] posted on 9-7-2015 at 18:37
stainless steel and hydrochloric acid purification


My problem is the separation of metal ions from each other including chromium and iron chloride from a solution that was gotten from the reaction of stainless steel wool and 9 molar hydrochloric acid. I am sure that the green nature of the solution is from chromium chloride and this is a unwanted impurity for my needs.

After the mixture is filtered and crystallized what is the best way to separate the products?




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[*] posted on 9-7-2015 at 20:20


First I'd oxidize them to (III) with hydrogen peroxide, next boil off the water, then heat the two chloride hydrates until they liberate hydrogen chloride gas and then their water. Now you have a mixture of oxides of iron (III) and chromium (III), treat this with hydrochloric acid, the iron oxide will dissolve but the chromium oxide will not.



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[*] posted on 10-7-2015 at 19:29


After oxidizing the salts with hydrogen peroxide is it possible to extract the iron (III) chloride with acetone and leave the chromium (III) chloride behind?



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[*] posted on 10-7-2015 at 20:02


Quote: Originally posted by SimpleChemist-238  
After oxidizing the salts with hydrogen peroxide is it possible to extract the iron (III) chloride with acetone and leave the chromium (III) chloride behind?

Not while they are in solution, since of course acetone is miscible with water. Also, Iron(III) chloride cannot be dehydrated to anhydrous iron chloride by heating, so you can't go that route. You *might* be able to boil off enough water to get the iron and chromium to crystallise out though, and try an extraction with that.
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[*] posted on 10-7-2015 at 21:18


You could also oxidize the Cr to chromate with hypochlorite and separate it that way, through fractional crystallization. And that way you also get some useful chromate out of it.



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[*] posted on 10-7-2015 at 21:46


What is the point of this exercise? You primarily have a solution of iron, nickel, and chromium salts. Which are you looking to recover and which are you not interested in?

Assuming the Chromium is in the +3 oxidation state, addition of ammonia will prpecipitate iron oxides and most of the chromium as the hydroxide. The solution will contain mainly nickel and a small amount of chromium.

Treating the residue with sodium hydroxide solution will dissolve the chromium hydroxide and leave behind the iron. Or if you treat the initial solution with NaOH, you will produce a solution of chromium and a sludge of hydrous iron oxides and nickel hydroxide.

If you want iron salts from this mess, why on earth did you not start with regular steel wool. If you wanted nickel, perhaps coins would have been a better starting place.
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[*] posted on 11-7-2015 at 02:47


Quote: Originally posted by SimpleChemist-238  
After oxidizing the salts with hydrogen peroxide is it possible to extract the iron (III) chloride with acetone and leave the chromium (III) chloride behind?


It is possible to extract the iron from solution with ether.
You need an excess of HCl to get the extraction to work.
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[*] posted on 11-7-2015 at 12:06


My extraction with acetone would happen after the solution crystallized. The iron would dissolve in the acetone and leave behind the chromium and nickel. I don't believe there is much nickel in the solution because the steel I used is very low grade.



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